Use of the FBX dosemeter for the calibration of cobalt-60 and high-energy teletherapy machines.

The doses from the cobalt-60 teletherapy machines were measured using the FBX and secondary-standard dosemeters of Farmer-Baldwin type. The FBX dosemeter contained 0.20 mM ferrous ammonium sulphate, 5.0 mM benzoic acid and 0.20 mM xylenol orange in 0.05 N sulphuric acid. The values were compared with the values from a Fricke dosemeter and a graphite chamber used as primary standards. The values of the FBX, Fricke and graphite chambers agreed. There were, however wide differences among the different secondary-standard dosemeters themselves and with the FBX dosemeter. The FBX dosemeter was used for the measurement of central axis depth dose distributions for 5, 8, 10, 20 and 30 MeV electron and 42 MV x-ray beams.

Absorption characteristics of xylenol orange.

Absorption characteristics of Xylenol Orange have been reinvestigated for the purpose of its spectrophotometric estimation. The molar absorption coefficient of Xylenol Orange at 580 nm and pH 10.0 is 3.12 x 10(4) l.mole(-1), cm(-1).

Determination of fluoride in zinc concentrates, processing products and solutions with an ion-specific electrode.

Determination of fluoride in hydrometallurgical zinc-plant processing products and solutions with a fluoride-ion electrode is described. Various types of buffers were tested, to find a suitable common buffer for use in analysis of all types of substances generated at the zinc plant. The method involves decomposition of samples either by fusion with sodium hydroxide or by leaching with perchloric acid to bring fluoride into solution. The fluoride concentration is measured directly with a fluoride-specific electrode. In standard addition tests 100% recovery was obtained when a citric acid/sodium nitrate buffer was used. Validation tests gave satisfactory results.

Studies on Pogonophora. 4. Fine structure of the cuticle and epidermis.

The fine structure of the integument in several species of Pogonophora has been examined by electron microscopy. The cuticle over the main body is composed of several layers of orthogonally arranged fibres embedded in an amorphous matrix. It is regularly traversed by microvilli from underlying epidermal cells. Toothed bristles of the annuli and setae of the anchor are composed of closely packed fibrous cylinders wrapped in a cortical material. In fine structure the cuticle, setae, toothed bristles (or setae) and setal sacs forming the setae closely resemble the corresponding structures in annelids. The cuticle is maximally thick over the forepart (protosome + mesosome) ; it is very thin and non-fibrous over the surface of the metameric papillae and over extensive areas of post-metameric trunk. The possibilities of a collagenous nature of the cuticle fibres and their mode of secretion by the epidermal cells are discussed. The organization of various cell-types forming the epidermis over the entire animal is examined. Possible functions of these cell-types are discussed. Notable amongst these are 'possible zymogen cells' and some absorptive cells. The intriguing question of nutrition in these gut-less tubiculous animals is re-examined in the light of present observations.

Fine structural organization of the spermatheca in the cockroach, Periplaneta americana.

The detailed structure of the cockroach spermatheca is described and discussed firstly as an example of an insect integumentary gland, and secondly, from the standpoint of its role in reproduction. The gland comprises a cortical rank of separate secretory units, each associated with an epithelial duct cell responsible for receiving secreted materials and transporting them through the cuticular intima lining the reproductive tract. Secretory activity is cyclic, and the probable mode of elaboration and release of secretory material is described, together with the fine structure of the markedly differing intimas associated respectively with the glandular and conducting units.

The x-ray microanalysis of frozen-hydrated sections in scanning electron microscopy: an evaluation.

The present status of the technique to measure concentrations of electrolyte elements and dry mass in or approximately 1 mum thick frozen-hydrated sections of soft biological tissues with electron probe X-ray microanalysis in a scanning electron microscope is critically reviewed. The technique is to quench-freeze fresh specimens to less than -180 degrees C, cut approximately 1 mum thick hydrated cryosections ( less than or equal to -70 degrees C), transfer on to a cold stage (less than -170 degrees C) of a suitable microanalytical arrangement, obtain scanning transmission images to identify the cell and tissue compartments, locate an electron probe (several mum2 to 100 nm) on the areas of interest and collect X-ray quanta. The X-ray quanta collected with suitable spectrometers (WDS and EDS) and processed with a computer using a comprehensive programme based on continuum normalization procedures ('Hall' programme). The cryosections are analysed first in a hydrated state and second after dehydration within the microanalyser column to obtain directly elemental concentrations in muM kg-1 wet wt and muM kg-1 dry wt of the compartments identified under the beam. The local water-fractions are estimated and the elemental concentrations converted into muM 1(-1) water. In the past 7 years the technique has been applied to obtain fully quantitative information on Na, K, Cl, P, S, Ca and H2O in more than ten types of tissue.

The organization of the central nervous connectives in Anodonta cygnea (Linnaeus) (Mollusca : Eulamellibranchia).

The cerebro-visceral connective of Anodonta cygnea comprises a non-cellular neural lamella, a few randomly distributed glial elements, and axons, together with an extensive extracellular system. The axons are relatively small, the majority being less than 2.0 micro in diameter. The neural lamella is underlaid by a thin layer of peripheral glial processes. The membranes of the proximate glial processes do not reveal any junctional complexes at this level. In addition to glycogen and fat deposits, the glial cytoplasm contains abundant 'glial granules' which in histochemical tests react like mucoproteins. The extracellular space appears to be freely accessible, for apart from the neural lamella no other visible structures are interposed between it and the fluid surrounding the connective. These structural findings are discussed in relation to the available evidence concerning the ability of axons to function in preparations bathed in low-sodium media.

Effect of experimental diabetes on the activities of hexokinase, glucose-6-phosphate dehydrogenase and catecholamines in rat erythrocytes of different ages.

Hexokinase and glucose-6-phosphate dehydrogenase were assayed in various circulating age fractions i.e., young, middle-aged and old red cell from control, diabetic and insulin-treated diabetic rats. An increase in the activity of hexokinase was observed in three age-wise separated fractions of red cells from diabetic animals in comparison to control. The activity of glucose-6-phosphate dehydrogenase on the other hand decreased in separated ageing fractions of diabetic red cells when compared to control. Reversal of these two enzymes were observed in insulin-treated diabetic rats. The levels of glycosylated haemoglobin and catecholamines were found to increase with ageing red cells in controls and also increased in red cells plasma.

Choice of antibiotics for empiric treatment of serious infections.

We have compared the in vitro activity of commonly used aminoglycosides--Gentamicin and Amikacin with Ciprofloxacin to determine whether the latter has any role in the empiric treatment of serious bacterial infections. Our results indicate that ciproloxacin was comparable or had a better activity than gentamicin or Amikacin against clinical isolates. As it can be administered orally, hospitalization can be avoided in a large number of patients.

Multidrug resistant Salmonella typhi in Delhi.

In 1990, we isolated 158 strains of Salmonella typhi from blood cultures of patients suffering from typhoid fever. Seventy nine (50%) of these isolates were found to be simultaneously resistant to chloramphenicol, ampicillin and cotrimoxazole. These strains were also resistant to streptomycin and tetracycline, but sensitive to gentamicin, amikacin and cephalexin. The minimum inhibitory concentrations of chloramphenicol and trimethoprim for a representative number of these strains were found to be greater than 1024 micrograms/ml and greater than 128 micrograms/ml respectively. Majority of the multidrug resistant (MDR) strains tested against cefotaxime (23/23), ciprofloxacin (38/38) and amoxycillin plus clavulanic acid (23/24) were sensitive to these drugs.

Adenosine deaminase activity in typhoid fever.

Serum adenosine deaminase (ADA) activity was determined in 41 patients of typhoid fever and 15 normal controls. The mean ADA activity was significantly raised in typhoid fever patients as compared to controls (p < 0.001). The peak enzymatic activity was observed in the first week of illness. Complicated patients had lower mean ADA activity at diagnosis as compared to uncomplicated group and they showed a rise in enzyme level during defervescence, repeated in a few cases. A significant correlation between serum ADA activity and lymphocyte percentage was found (r = 0.4245, p < 0.001). It is concluded that ADA activity in typhoid fever patients not only indicates immunity but also has a prognostic value.

Susceptibility of clinical isolates to cephalexin, cefazolin and cefotaxime.

Three hundred and seventeen recent clinical isolates were tested for in vitro susceptibility to the three cephalosporins available in India--cephalexin, cefazolin and cefotaxime by the Kirby--Bauer disc diffusion method. Cefazolin was the most effective cephalosporin against Gram positive cocci (71.8% sensitive) followed by cefotaxime (62.7%) and cephalexin (52.7%). Cefotaxime was very effective against commonly isolated Gram negative bacilli with only 10 (8.8%) isolates being resistant to it while 44 (39%) and 65 (57.5%) were resistant to cefazolin and cephalexin, respectively. All isolates of Pseudomonas aeruginosa were resistant to cephalexin and cefazolin and only 29 (32.6%) were sensitive to cefotaxime.